The sea as climate protector

The oceans absorb immense amounts of CO₂ each year. Graphic: Hereon/ Ha Thi Minh Hagemann

In the APOC collaborative project funded by the German Federal Ministry of Education and Research (BMBF), insights have been gained since April of this year that ultimately also affect human survival. The BMBF-funding contains 2,65 Millionen Euro until 2024. The main task of Hereon in APOC is to quantify organic carbon pools, simulate and quantify past and future anthropogenic influences on POC cycling and sequestration in the North Sea. "Using a broad range of analytical methods, we will determine how sedimentation conditions, origin and reactivity of organic carbon behave," says Dr. Wenyan Zhang of the Hereon Institute of Coastal Systems - Analysis and Modeling, who is project coordinator together with Prof. Sabine Kasten of the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (AWI). The additional project partners involved are GEOMAR Helmholtz Centre for Ocean Research Kiel, BUND and the University of Hamburg. POC refers to the mass of carbon in particulate organic matter. It is present in oceans including coastal shelf seas in partially decomposed detritus as well as plant material and pollen. The oceans annually absorb an amount of CO₂ equivalent to 40 percent of emissions since industrialization. Phytoplankton produce organic carbon by absorbing dissolved inorganic carbon, such as CO₂, through photosynthesis in the sunlit ocean.

Data that allow classification

"The physical and biogeochemical processes that control the mineralization and deposition of POC, and how they have changed and are changing over the past 100 years - that's what we want to find out," says Wenyan Zhang. He and his colleagues are using an integrated modeling system called GCOAST, which Zhang helped develop, 3D modeling included. The system is open source, which means that anyone can use it and develop it further.

What role does POC play in the North Sea food web? What about the interactions between POC and fine-grained lithogenic particles in the ocean, especially with regard to deposition and storage? And to what extent human activities have altered the storage capacity of POC in sediments? GCOAST will be used to simulate the current, past, and future turnover of POC and to interpret human-induced changes due to, for example, climate change, bottom trawling fisheries, and resource extraction in the North Sea.

The goal: understanding and changing

The results can be used to formulate options for action for decision-makers. Only by understanding what is happening in the North Sea can certain developments be halted or delayed while preserving the North Sea's current capacity to deposit and store POC. As is common with modeled projections, this includes the development of future scenarios.

Knowledge transfer is central to the researchers' work. "It's important to map and inform about the consequences of human actions," Zhang says. These, in turn, are then translated to regional, national and EU bodies. Lastly, the research results will be placed in the context of current marine policy, combined with suggested options for action to the relevant bodies, as well as extensive preparation for the public. In this way, modeled data can help to influence climate change.